The benefits of breastfeeding extend long beyond childhood, a decades-long study finds. Researchers have been keeping tabs on a group of Brazilian children since 1982, and recently, they checked in with some 3,500 of them to see how they're doing as adults. Interviews and an IQ test found that those who breastfed had higher IQs and were earning more money, the Guardian reports. In fact, a longer period of breastfeeding was associated with particularly good results: Those babies who had breastfed for a year ended up pulling in about $100 more per month as adults than did those who had breastfed for less than a month. They also had IQs that surpassed the shorter-term breastfeeders by four points.
The researchers used data from a wide range of socioeconomic backgrounds, the Guardian notes, and they worked to control for factors like maternal education, babies' birth weight, mothers' smoking, and more. Still, the scientists say that other influences could be at play, and the lead researcher tells the New York Times that he doesn't "want to terrify people who did not breastfeed or who breastfed for a short time." In fact, another recent study questions the idea that IQ and breastfeeding are linked: A researcher in the Netherlands tells MedicalResearch.com that other variables—including "sociodemographic factors, parental lifestyle, and, most importantly, maternal IQ" may explain the connection. Still, she agrees that "breastfeeding is important for overall optimum growth of children." (A lactation expert recently explained why pumping and breastfeeding aren't equivalent.)